Exposure control apparatus

ABSTRACT

A photographic exposure control mechanism having two shutter blades, one for initiating and one for terminating a photographic exposure. Both blades are retained in a spring loaded condition prior to an exposure. That blade terminating exposure is retained in an open position throughout an exposure interval by a latch which is moved into engagement therewith simultaneously with the movement of an energized electromagnet. Deenergization of the electromagnet releases the blade to terminate an exposure.

United States Patent- [72] inventor Alfred H. Bellows Cambridge, Mass. [2|] Appl. No. 749,449 [22] Filed Aug. 1,1968 [45] Patented Jan. 26, 1971 [73] Assignee Polaroid Corporation Cambridge, Mass. a corporation of Delaware [54] EXPOSURE CONTROL APPARATUS 4 Claims, 2 Drawing Figs.

[52] US. Cl 95/53, 95/60 [51] Int. Cl G03b 9/16 [50] Field of Search 95/53, 53EO, 60

[56] References Cited UNITED STATES PATENTS.

3,386,363 6/1968 Rentschler 95/53 3,461 ,784 8/1969 Burgarella 95/53X 3,461,785 8/1969 lvester 95/53X 3,470,808 10/ 1969 Bloemendaal 95/53X Primary Examiner-John M. Horan Assistant ExaminerMichael Harris Attorneys-Brown and Mikulka, William D. Roberson and James L. Neal ABSTRACT: A photographic exposure control mechanism having two shutter blades, one for initiating and one for terminating a photographic exposure. Both blades are retained in a spring loaded condition prior to an exposure. That blade terminating exposure is retained in an open position throughout an exposure interval by a latch which is moved into engagement therewith simultaneously with the movement of an energized electromagnet. Deenergization of the electromagnet releases the blade to terminate an exposure.

PATENTEU JAN26 I97! INVENTOR. 6m

and and.

m M M ATTORNEYS FIGZ.

EXPOSURE CONTROL APPARATUS SUMMARY OF THE INVENTION Photographic exposure control apparatus of this invention involves first and second shutter blades biased for exposure influencing movement and an electromagnetically controlled latch for releasably holding the second blade against exposure influencing movement for a predetermined interval after release ofthe first blade. I

The latch mean sand the electromagnetic means for controlling the latch are movably mounted adjacent the second blade for releasably retaining it against the exposure influencing movement subsequent to exposure influencing movement of the first blade. The latch means and the electromagnetic means are mounted in a manner permitting them'to be moved either as a single unit relative to the second blade or individually relative to each other and to the second blade. The latch means is engageable with the second blade and biased out of engagement therewith; the electromagnetic means is continuously biased for movement into contiguity with the latch means. According to the sequence of operation, a solenoid forming part of the electromagnetic means is energized while the electromagnetic means is in contiguity with the latch means thus causingthe latch means and the electromagnetic means tobe in magnetic engagement; the electromagnetic means is then advanced to draw the latching means toward and into latching engagement with the second blade. During advancement of the electromagnetic means, both the electromagnetic means and the latch means move as a single unit, due to the aforesaid magnetic engagement between them. Subsequent to' movement of the-latching means .into latching engagement with the second blade, the first blade is released to initiate photographic exposure. During photographic exposure, the electromagnetic means is held in its advanced position to maintain the latching means in latching relationship with the second blade. A predetermined timed interval after exposure initiation, the coil of the electromagnetic means is deenergized to interrupt magnetic engagement between the electromagnetic means and the latch means. The latch means is then free to move according to its bias, out of latching engagement with the second blade, thus releasing the second blade for exposure influencing movement to terminate exposure. Subsequent to exposure, the electromagnetic means is permitted to move back into contiguity with the latch means. A reset mechanism returns the shutter blades to the positions which they occupied previous to photographic exposure production. I I

It is a primary object of this invention to provideimproved electromagnetically controlled latch means for influencing shutter blade movement in a photographic camera.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a preferred embodiment of this inventiomand FIG. 2 is a schematic wiring diagram of electrical circuitry usable with the apparatus of FIG. I.

DETAILED DESCRIPTION or rue DRAWINGS The apparatus of FIG. I-includes base plate forming exposure aperture 12, shutter means 14 for blocking and unblocking movement relative to aperture 12, shutter drive means 16, latch means I8, electromagn'etic'means l9, retaining and advancing means and actuating means 22.

Shutter means 14 includes opening blade 24 and closing blade 26, both pivotally mounted upon support 28. The opening blade is pivotally movable from a resetposition wherein it blocks the exposure aperture to a rundown position wherein it unblocks the exposure aperture to initiate a photographic exposure. Aperture 30 formed by the opening blade moves into superposition with the exposure aperture when blade 24 moves to its rundown position. Opening blade 24 also supports nonconductive, switch operating projection 23 and a screw rack 32 along its peripheral edge. The rack assumes a circular configuration having pivotal support 28 as its center. Stop means 34 is located adjacent the rundown'position of opening blade 24to terminate exposure influencing movement of the blade. Projection 25 extends from blade 24 for cooperation with closing blade 26. Closing blade 26 includes offset 27 and is movable from a reset position wherein it unblocks the exposure aperture to a rundown position wherein it blocks the exposure aperture for terminating exposure. As seen in FIG. 1, blade 24 blocks aperture 12 and blade26 unblocks aperture Shutter drive means 16 comprises two springs. Spring 36 is wound about support 28 and attached to opening blade 24 by anchor 38 and fixedly mounted to base plate 10 by anchor 40 for continuously biasing and driving the opening blade clockwise from its reset position to its rundown position. Spring 42 is wound about support 28 and attached to the closing blade by anchor 44 and fixedly mounted to base plate 10 by anchor 40 for continuously biasing and driving the closing blade clockwise from its reset position to its rundown position.

Latch means 18 and electromagnetic means 19 cooperate to hold closing blade in its aperture unblocking position after movement of the opening blade to its aperture unblocking position. The electromagnetic means involves an electromagnet and electrical control circuit 50. The electromagnet includes U-shaped core 52, support 53 formed integrally therewith and a' solenoid in the form of electrically energizable coil 54 wound around one leg of the core. Latch means 18 comprises pivotally mounted magnetizable keeper means 56 having upstanding portion 57 and latching projection 59. Fortion 57 is magnetically cooperable with core 52. Projection 59 is mechanically engageable with offset 27 on blade 26. Elements 52, 54 and 56 cooperate to form a magnetizable latch. Support 53 for core 52 and keeper means 56 are mounted by pin for pivotal movement relative to each other and to plate 10. Core 52 defines a pair of free ends 58 which are coplanar and cooperate with portion 57 of magnetizable keeper 56. The core and the keeper are positioned adjacent the reset position of the closing blade so that projection 59 is located for engagement with offset 27 when the closing blade is in the aforesaid reset position. Spring means 61 and spring means 63 continuously bias keeper 56 and support 53, respectively, counterclockwise relative to plate'l0 to a position wherein keeper 56 abuts stop 65 and ends 58 of core 52 firmly abut portions 57 of keeper means 56. When in abutment, keeper 56 and core'52 define a complete magnetic circuit. Energization of coil 54 applies a sufficient magnetomotive force to the magnetic circuit to hold the keeper securely against the core. I I a Control circuit 50, shown in FIG. 2, incorporates timing circuit and trigger circuit 62, trigger circuit 62 incorporating coil 54. Timing circuit 60 includes photoresponsive element 64, such as a cadmium sulfide photocell or the like, exposed to light from a scene being photographed and characterized by resistance related to the level of scene brightness and capacitor C Element 64 and capacitor D, are connected in series between terminals 66 and 68. Circuit 60 constitutes an integrating circuit responsive to the light level of the scene being photographed, the input tenninal of which is at 66 and the output terminal of which is at '70. Trigger circuit 62 may be,

for example, a transistorized two-stage Schmitt-type trigger circuit responsive to the output voltage of timing circuit 60. A

circuit of this type is shown and fullydescribed in US. Pat. No. 3,241 ,47l, issued to John P. Burgarella on Mar. 22, 1966 Trigger circuit 62 has an input that is a nonnally nonconducting stage including transistor 0, and an output that is a normally conducting stage including transistor 0,. While thetwo stages of the trigger circuit are referred to as normally notconducting" and "normally conducting, it should be obvious that this characterization-isapplicable only when a voltage source is supplied across terminals 66 and 68. Voltage source 72 is shown in the form of a battery of potential E connected between terminals 66 and 68 through normally open switch 8,.

Switch S, is closed to apply voltageacross terminals 66 and 68 during initiation of exposure producing operation of the apparatus, in a manner hereafter to be described; Switch S, mustposition to a rundown position for terminating exposure. The I second blade is releasably retained in its reset position after movement of the first blade from its reset position by the electromagnet. Circuit means 50 operates to cut off the flow of current to the electromagnet to free the second blade for movement to its rundown position a predetermined timed interval after movement of the first blade from its reset position toward its rundown position. Movement of the first blade from its reset position permits switch S to open to initiate the timing operation and thereby control-the time of release of the second blade.

At the instant switch S, is closed, and before switch S, is opened by movement of the first blade from its reset position, a ground potential voltage is applied at terminal 70. When switch S, is opened, there appears at output terminal 70 a voltage which changes from the initial value, e.g., ground potential, to a predetermined value during a period of time dependent upon the value of capacitor Q, and the resistance of photoresponsive element 64. When the potential at terminal 70 reaches the aforesaid predetermined value, the normally notconducting transistor Q, is forward biased and conducts whereupon the normally conducting transistor 0, is switched to its not-conducting stage. When transistor 0, is switched to its not-conducting stage, coil 54 of the electromagnet is deenergized to release the second blade for exposure terminating movement. Voltage is applied across terminals 66 and 68 for the duration of the exposure interval by maintaining switch S, in its closed condition for at least as long as the longest exposure interval contemplated.

Retaining and advancing means includes worm gear 80, electrical drive means 82, drive shaft 84 and universal joint 86. Drive means 82 is mounted on plate 10 and rotatably supports one end of drive shaft 84. Worm gear 80 is mounted upon the drive shaft for rotation thereby and for movement into and out of cooperating relationship with rack 32. Universal joint 86'enables the drive shaft to rotate gear 80 and also permits it to flex in a manner to permit the aforesaid movement of gear 80 into and out of cooperating relationship with rack 32.

Drive shaft 84 and gear 80 are rotatable in the direction of arrow 81 by drive means 82 aftermovement of blades 24 and 26 to their rundown positions. Gear 80 cooperates with rack 32 to advance opening blade 24 in a counterclockwise direction against the bias of drive spring 36 toward and to its reset position; projection 25 on the opening blade engages blade 26 to advance it counterclockwise against the bias of drive spring 42 toward andto its reset position. Circuit 100 for controlling the operation of drive means 82 may include rotary electric motor, designated 82, switch S, and switch 5,, all connected in series with battery 72. According to this arrangement, circuit 100 is operative only when both switch 8, and S, are closed, as will later be described.

Actuating means 22 includes lever 88 and reciprocal pin 102. Lever 88 is pivotally mounted to base plate 10 by pivot pin 90 and biased for clockwise movement by spring means 92.!lnp'ut 94 adjacent one end of lever 88 may be manually manipulated for initiating operation of the apparatus. Seat" 96 adjacent either end of lever 88, beneath end 98 of drive shaft 84, is for lifting the drive shaft to remove gear 80 from rack 32. Lever 88 also operates switches S, and S Switch S, is biased opened and is closable by lever 88; switch S, is normally closed and may be opened by operation of lever 88. pin 102 is reciprocally mounted on plate 10 and extends from beneath lever 88 to upturned extension 104 of electromagnetic means 19. Slots 106 cooperate with studs 108 extending from plate 10 to slidably mount the pin. Spring means 110 biases the leverupward to a position wherein it abuts lever 88 and is displaced from upturned extension 104 of electromagnetic means 19.

The locations of switches 5,, S S and 8,, discussed above, will now be described.

Switch S, includes resilient terminal 1 12 and terminal 114. Terminal 112 extends into engagement with lever 88 and terminal 114 is disposed beneath terminal 112, theterminals being biased open. Counterclockwise movement of lever 88 deflects terminal 112 into contact with terminal 114 to close switch 8,. Clockwise movement of the lever permits terminal 112 to return to its relaxed position to open switch 5,.

Switches S and S are mountedadjacent the position occupied by switch operating projection 23 of opening blade 24 when theshutter blades are in their reset positions. Switches S and 5, include terminals 116 and 118 and terminals 120 and 122 respectively. Terminal 116 of switch S, is resiliently biased out of contact with terminal 118; terminal 120 of switch S is resiliently biased into contact with terminal 122. Terminals 116 and '120 extend into the path of nonconductive projection 23 of opening blade 24 such that, when the opening blade in its reset position, projection. 23 engages both terminals 116 and 120 and flexes them, terminal 116 being moved into contact with terminal 118 to close switch S and terminal 120 being moved from contact with terminal 122 to open switch S The switch terminals are located so that, as projection 23 moves biased out toward and to terminals 116 and 120, switch S, will be closed just prior to the opening to switch S 9 Switch S nd is mounted adjacent corner 124 of lever 88 and includes relatively rigid terminal 126 and resilient terminal 128. The resilient terminal is biased into contact with the rigid terminal to bias switch S closed and engageable by corner 124. Initial counterclockwise movement'of lever 88 deflects terminal 128 to open switch S.,; similarly, final clockwise movement of lever 88 pennits return of resilient terminal 128 to its position in contact with terminal 126. Operation of the apparatus will now be described. FIG. 1 illustrates the apparatus in its reset condition. Opening blade 24 blocks exposure aperture 12 and closing blade 26 unblocks exposure aperture 12. The opening blade is retained in its reset positions by engagement between retaining an advancing means 20 and rack 32. Projection 25 extending from blade 24 engages blade 26 for retaining it in its reset position. Spring means 61 retains latch means 18 in a counterclockwise rotated position out of engagement with offset 27, abutting stop 65. Electromagnetic means 19 is maintained in a counterclockwise rotated position wherein faces 58 of core 52 are contiguous portion 57 of latch means 18 by the action of spring means 63. Switches S, and S, are closed; switches S, and S, are open.

To initiate the operation, pressure is applied to input 94 for rotating lever 88 counterclockwise against the bias of spring 92. Initial rotation of lever 88 substantially simultaneously closes switch S, and opens switch S Closure of switch S, completes circuit 50 to energize coil 54 and establish magnetic engagement between portion 57 of latch means 18 and U-shaped core 52 of electromagnetic means 19. Voltage applied across temiinals 66 and 68 as long as lever 88 is maintained in its counterclockwiserotated condition. Since reaction time in depressing and releasing input 94, and the inertial by means 20, it will move to bring offset 27into seating relationship with projection 59. j

Further counterclockwise rotation of lever88 brings seat 96 into position for lifting end 98 of drive-shaft 84 to thereby disengage gear 80 and rack 32. Offset 27 is configured to provide overtravel for projection '59 after the projection moves to its holding position so that the projection may continue to move while gear 80is being lifted.- Resilient stop 131 limits'move ment of shaft 84. Springs 36 and 42 simultaneously advance opening blade 24 and closing blade 26 clockwise. Blade 24 moves to its exposureaperture unblocking'position wherein aperture 30 in blade 24 is superposed with exposure aperture 12. Blade 26 moves to-close the space between ofiset 27 and projection 59 and bring the offset into seating relationship with the projection. Blade-26 is then retained in'its aperture unblocking position by the cooperation between latch means 18 and electromagnetic means 19. When offset 27 abuts projection 59, shock forces resulting from the impact are directed substantially along portion 57 of latch means 18 and thereby do not tend to drive latch means 18 out of magnetic engagement with electromagnetic means 19. a a

initial aperture unblocking movement of opening blade 24 causes the opening blade to move out of engagement with and switch S close.

The opening of switch 8, initiates the timing operation discussed above. At the end of thetimed interval, the duration of which is controlled by circuit means 60 in accordance with the light level of the scene being photographed in the manner aforesaid, coil 54 of the electromagn'et is deenergized thus interrupting themagnetic attraction between core 52 and portion 57 of keeper means 56. Spring means 61 draws latch means 18 counterclockwise against stop 65 and thereby removes projection 59 from retaining relationship with offset 27 to release closing blade 26 for clockwise aperture blocking movement from its reset position toward its rundown position in accordance with the bias of spring 42. Clockwise movement of blade 26 continues until an edge thereof engages projection 25 on blade 24, projection 25 having moved to a position clockwise of exposure aperture 12 during aperture unblocking resilient terminals 116 and 120 to 'pennit switch S, to open movement of blade 24. In its rundown position, closing blade 26 blocks the exposure aperture and thereby terminates the exposure interval. i

Closure of switch S, occurs just prior to the opening of switch 8,. However, closure of switch S, does not complete circuit 100 since switch S is being held open by the position of lever 88. i

The pressure applied to input 94 is released subsequent to exposure termination. Spring 92 rotates lever 88 clockwise about pivot-pin 90. Counterclockwise movement of lever 88 sequentially brings gear 80 into operative engagement with rack 32, permits spring means 110 to lift pin 102 from engagement with upturned portion 104 of electromagnetic means 19, closes switch S and opens switch 8,.

Upward movement of pin 102 permits spring means 55 to rotate electromechanical means 19 counterclockwise and return free ends 58 thereof to a position contiguous portion 57 of latch means 18. Spring means 63 continues to press free ends 58 of core 52 against portion 57 of the latch means and thereby maintains the latch means and the electromagnetic means in firm contact so that upon subsequent energization of coil 54, magnetic engagement will be established between latch means 18 and electromechanical means 19. The opening of switch S, inactivates control circuit 50. Closure of switch S tion wherein it unblocks exposure aperturevAs the blades move into their reset positions, offset 27 moves tothe appropriate position relative to projection. 59 for subsequent engagement thereby and switch operating projection 23 engages terminals 116 and 120 to move them'against their bias. Terminal 116 is moved into contact-with terminal 118 to close switch S5 and terminall20 is moved out of contact with terminal 122 to open switch S The opening of switchS deenergizes circuit 100 to cut off motor'82. Engagement between gear and rack 32 retains the opening and closing blades in their reset positions. The apparatus is thus completely reset for another exposure producing operation.

The terms up, down, clockwise, counterclockwise and the like are used in the foregoing disclosure to describe movement of various elements as seen in FIG. 1 and'are not intended to be used in a limiting sense.

Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that'all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Iclaim:

1. Exposure control apparatus for a photographic camera comprising:

a. shutter means mounted for movement from a first to a final position for influencing photographic exposure;

b. latch means, at least a portion of which is magnetizable,

movable into holding relationship with said shutter means for preventing movement thereof from said first to said final position and biased out of said holding relationship; c. movably mounted electromagnetic means biased for movement to a position'contiguous the magnetizable portion of said latch means for magnetic engagement with said latch means when said .electromagnetic means is energized; actuating means operable to energize and then move said electromagnetic means for moving said latch means into said holding relationship with said shutter means to thereby prevent exposure influencing movement of said shutter means; and e. means for deenergizing said electromagnetic means to interrupt magnetic engagement between said electromagnetic means and said latch means thereby to permit movement of said latch means out of holding relationship with said shutter means and release said shutter means for movement from said first to said final position. 2. Exposure control apparatus according to claim 1 wherein:

a. said latch means comprises:

1. an elongated magnetizable bar defining a substantially planar surface directed toward said electromagnetic means; and

2. means, releasably engageable and b. said electromagnetic means comprises:

l. a substantially U-shaped magnetizable core defining substantially coplanar endsurfaces;

a. means biasing said core toa position wherein said coplanar surfaces about said planar surface of said bar for magnetic engagement with said bar when said core is magnetized;

3. energizable solenoid means wound upon a leg of said U-shaped core for magnetizing said core when energized; and

with said shutter means;

b. first exposure influencing means movable from a first position wherein it blocks said aperture to a second position wherein it unblocks said aperture for initiating a photographic exposure interval; Y

c. second exposure influencing means movable from a first position wherein it unblocks said aperture to a second position wherein it blocks said aperture for terminating said exposure interval; g

d. means for releasably retaining said first and second means in their respective aperture blocking and unblocking positions; t

e. latch means, at least a portion of which is magnetizable, for releasably holding said second means in its aperture unlocking position, said latch means being movable into and out of holding relationship with said second means and biased out of said holding relationship; f. electromagnetic means magnetically engageable with said latch means and movable for drawing said latch means,

against the aforesaid bias, into holding relationship with said second means prior to release of said first and second means by said retaining means to thereby prevent movement of said second means from its aperture unblocking position while permitting movement of said first means to its aperture unblocking position when said first and second means are released by said retaining means, thereby to initiate exposure; and

t g. means for interrupting the magnetic engagement between said magnetic means and said latch means to permit movement of said latch means out of holding relationship with said second means under vthe influence of the aforesaid bias, thereby to permit movement of said second means to its aperture blocking position to terminate exposure.

4. Exposure control apparatus according to claim 3 further comprising:

a. means continuously biasing said electromagnetic means for movement into contiguity with said magnetizable por tion of said latch means for magnetic engagement therewith when said electromagnetic means is energized; and j i b. means operable to energize and subsequently move said electromagnetic means for drawing said latch means into holding relationship with said second means. 

1. Exposure control apparatus for a photographic camera comprising: a. shutter means mounted for movement from a first to a final position for influencing photographic exposure; b. latch means, at least a portion of which is magnetizable, movable into holding relationship with said shutter means for preventing movement thereof from said first to said final position and biased out of said holding relationship; c. movably mounted electromagnetic means biased for movement to a position contiguous the magnetizable portion of said latch means for magnetic engagement with said latch means when said electromagnetic means is energized; d. actuating means operable to energize and then move said electromagnetic means for moving said latch means into said holding relationship with said shutter means to thereby prevent exposure influencing movement of said shutter means; and e. means for deenergizing said electromagnetic means to interrupt magnetic engagement between said electromagnetic means and said latch means thereby to permit movement of said latch means out of holding relationship with said shutter means and release said shutter means for movement from said first to said final position.
 2. Exposure control apparatus according to claim 1 wherein: a. said latch means comprises:
 2. means releasably engageable with said shutter means; and b. said electromagnetic means comprises:
 3. energizable solenoid means wound upon a leg of said U-shaped core for magnetizing said core when energized; and
 3. Exposure control apparatus for a photographic camera comprising: a. means forming an exposure aperture; b. first exposure influencing means movable from a first position wherein it blocks said aperture to a second position wherein it unblocks said aperture for initiating a photographic exposure interval; c. second exposure influencing means movable from a first position wherein it unblocks said aperture to a second position wherein it blocks said aperture for terminating said exposure interval; d. means for releasably retaining said first and second means in their respective aperture blocking and unblocking positions; e. latch means, at least a portion of which is magnetizable, for releasably holding said second means in its aperture unlocking position, said latch means being movable into and out of holding relationship with said second means and biased out of said holding relationship; f. electromagnetic means magnetically engageable with said latch means and movable for drawing said latch means, against the aforesaid bias, into holding relationship with said second means prior to release of said first and second means by said retaining means to thereby prevent movement of said second means from its aperture unblocking position while permitting movement of said first means to its aperture unblocking position when said first and second means are released by said retaining means, thereby to initiate exposure; and g. means for interrupting the magnetic engagement between said magnetic means and said latch means to permit movement of said latch means out of holding relationship with said second means under the influence of the aforesaid bias, thereby to permit movement of said second means to its aperture blocking position to terminate exposure.
 4. means engageable by said actuating means to transmit movement of said actuating means to said electromagnetic means when said core is magnetized for moving said latch means to thereby move said means engageable with said shutter means into releasable engagement with said shutter means.
 4. Exposure control apparatus according to claim 3 further comprising: a. means continuously biasing said electromagnetic means for movement into contiguity with said magnetizable portion of said latch means for magnetic engagement therewith when said electromagnetic means is energized; and b. means operable to energize and subsequently move said electromagnetic means for drawing said latch means into holding relationship with said second means. 